The present invention relates to a method of improving the control behavior of an anti-lock control system, in particular, of improving the steerability of the automotive vehicle and the driving stability during cornering, wherein a vehicle reference speed is derived from the rotating behavior of the wheels of the automotive vehicles and criteria are obtained for identifying a cornering situation and the curve direction, and once a cornering situation is identified, the standard control mode is replaced by a special or curve control mode which already in the partial deceleration area causes a direct or a indirect reduction in brake pressure on the front wheel at the inner side of the curve and/or on the rear wheel at the inner side of the curve.
DE 34 13 738 C2 already discloses an anti-lock control system provided with a system for identifying a cornering situation also based on wheel slip measurement. To identify a cornering situation, the slip values on the wheels at one vehicle side are summed up and compared to the slip values on the wheels at the other vehicle side, generating a cornering identification signal as soon as the difference of the summed-up slip values exceeds a predetermined threshold value. Upon identification of a cornering situation, selective criteria, such as "select-low" or "select high" according to which the course of pressure in the individual brake pressure control channels of the said brake system is controlled, and threshold values for rendering the said selective criteria effective, are varied. In this way, the control will be adjusted to the varying conditions during straight-forward driving and during cornering.
DE 21 19 590 A1 teaches to generate a cornering identification signal with the aid of a lateral accelerometer, such as a mercury switch.
Moreover, it is already known in the art to extend the functions of an anti-lock control system by employing the system for improving the driving stability or deceleration stability in the curve. For this purpose, during Cornering or during a partial deceleration, i.e. in a deceleration process in which the threshold of response to the anti-lock control system is not achieved, a stabilizing moment about the vertical axis of the vehicle is created by specifically delaying the brake pressure build-up on the wheels at the inner side of the curve compared to the brake pressure on the wheels on the outer side of the curve ("Bremsanlage und Schlupf-Regelsystem der neuen 7-er Reihe von BMW" (Brake System and Slip Control System of the new BMW No. 7 series); ATZ 97 (1995), pp. 8-15, and "Bremsanlage und Schlupf-Regelsysteme der neuen Baureihe 5 von BMW" (Brake System and Slip Control Systems of the new BMW No. 5 series); ATZ 98 (1996), pp. 188-194. The information on the actual steering angle is derived--if no steering angle sensor is used--from the lateral acceleration which, in turn, is calculated from the wheel sensor signals.
Now, it is the object of the invention to avoid, in a control system exclusively evaluating the wheel rotating signals also for cornering identification, the disadvantageous effects of "errors in identification". For, exclusive reliance on the signals generated by the number of revolutions of the wheel may result in situations favoring errors in identification. This applies, for example, to cornering on :-split, i.e. on a varying right/left coefficient of friction if the inner side of the curve has a high coefficient of friction, while the outer side of the curve has a low coefficient of friction. In that situation, a stabilizing step interfering with the wheel allegedly on the inner side of the curve, could cause a destabilizing moment of yaw.